Still, FDA staff suggested updating Tamiflu's label to recommend that all patients, especially children, be closely monitored while on the drug. They also acknowledged that stopping treatment with Tamiflu could actually harm influenza patients if the virus is the cause of delirium, hallucinations and other abnormal behavior, such as aggression and suicidal thoughts.

Most of the instances of bizarre behavior are originating in Japan where the number of Tamiflu prescriptions is about 10 times that in the United States.